The rail vehicle system includes a travel rail having branch sections and merge sections. The branch section and the merge section have the same structure except that the travel direction in the branch section is opposite to the travel direction in the merge section. The branch section includes a straight lane and a branch lane with a curve. The merge section includes a straight lane and a merge lane with a curve. In the branch section or the merge section, a gap as a discontinuous portion of a travel surface is present. In order to reduce the impact when the rail vehicle passes the gap, it has been customary to provide auxiliary wheels inside the left and right travel wheels. In the specification, the shift from the state where the travel wheel rides on the ground to the state where the auxiliary wheel rides on the ground is referred to as the “wheel shift”.
In the case where the rail vehicle is on the straight lane of the branch section or the merge section, normally, the rail vehicle travels at high speed in comparison with the case where the rail vehicle is on the branch lane or the merge lane. If the wheel shift operation is performed when the rail vehicle travels at high speed, at the moment the auxiliary wheels land on the travel surface, an impact is applied to the travel surface. As a result, the travel surface is vibrated to generate vibration of the rail vehicle or noises. For example, the travel surface for landing of the auxiliary wheel has a triangular shape protruding toward the inside of the branch section or the merge section, and the rigidity of the travel surface is not sufficient. Since the auxiliary wheel lands on the front end of the travel surface, the travel surface can be vibrated easily. The vibration at the time of the wheel shift adversely affects the rail vehicle, the transported article, and the travel rail. Therefore, the rail vehicle cannot travel straight through the branch section or the merge section at high speed smoothly. The inventor studied to reduce the vibration which is generated when the rail vehicle travels straight though the straight lane of the branch section or the merge section, and achieved the present invention.